The miniature circuit breaker is an important electrical element used in low voltage power distribution industry and civilian equipments and is usually used in the terminal of low-voltage power distribution system. Currently, both domestic and foreign miniature circuit breakers realize the overload and short circuit protection of current by the thermomagnetic technology principle and solution, which not only has a poor short circuit breaking capacity but also causes high energy consumption, does not have adjustable protection features, and cannot be adapted to the motor protection. Therefore, the requirement of selective protection of the system cannot be satisfied, and the reliability of power supply is low.
With the construction of smart grid and the intellectualization of power grid at the client end, higher requirements for the reliability of the end power distribution system are raised, which objectively promotes the intellectualization demands of the miniature circuit breaker. In order to achieve the requirements of selective protection of the end power distribution system, the miniature circuit breakers with different structures were made in recent years. For example, selective requirements can be partially satisfied by using the product having contact structure of internal double-loop. However, in doing so, some protective characteristics cannot be adjusted, and the motor protection is not allowable. Moreover, the method of protective tripping that uses the traditional heating element to sense the overload current fails to solve the problem of energy loss. In addition, the existing miniature residual-current circuit breaker is assembled by a miniature circuit breaker and residual current tripping module. Due to the long width of residual current tripping module, the width modulus of the miniature residual current circuit breaker is significantly increased, so the volume of the power distribution box is relatively large.